Q) Which weighs more:-

A kilogram of feathers or a kilogram of iron?

DENSITY

What is Density?

Density is the Mass per unit Volume

Wood Water Iron

1 cm3 1 cm3 1 cm3

If you take the same volume of different substances, then they will weigh different amounts.

0.50 g 1.00 g 8.00 g

Q) Which has the greatest mass and therefore the most dense?

IRON

Cube Representations

1 m3 = 1 000 000 cm3

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 119

Density = MassVolume

g

cm3

g/cm3

d = m

V

Example:Q) A gold-colored ring has a mass of 18.9 grams and a volume of 1.12 cm3. Is the ring pure gold? (The density of gold is 19.3 g/ cm3.)

Density Equation:

d = m = 18.9g = 16.88 g/cm3

V 1.12cm3 No – it is not pure gold!

DENSITY OF A REGULAR SOLID

Find the Mass of the solid on a balance.Measure the three

lengths and calculate the Volume.

(i.e., V = l x w x h )Calculate the

Density.

4.0 cm

2.0 cm

3.0 cm

d = m = 240 =10.0 g/cm3

V 24 (2cm * 3cm * 4cm = 24 cm3)

m = 240 g

DENSITY OF AN IRREGULAR SOLID

Find the Find the MassMass of the solid on of the solid on a balance.a balance.Fill the Measuring Cylinder Fill the Measuring Cylinder with Water to a known with Water to a known VolumeVolume.. Add the Object.Add the Object. Work out the Work out the VolumeVolume of of Water that is displaced.Water that is displaced. Calculate the Calculate the DensityDensity..

50 cm3

80 cm3

m = 360 g d = m = 360 =12.0 g/cm3

V 30

What happens when you put an object in a fluid?

If the object is less dense than the fluid…

it floats

What happens when you put an object in a fluid?

If the object is more dense than the fluid…

it sinks!

What happens when you put an object in a fluid?

If the object is as dense as the fluid…

Neither floats nor sinks!